Length-adjustable telescopic tubes comprising an outer and an inner tube are used in support structures, in particular axle trailer or semi-trailer devices.
Such devices are known, for instance, from EP 1 104 369 B2. In this known device, a component that forms the common bearing block for the spindle and the transmission input shaft is connected on three sides to a tube of a telescopic tube unit, wherein the fourth side is arranged at a distance to the last wall of the tube. This makes it possible to achieve a particularly compact design of the supporting device since part of or the entire transmission may be accommodated for driving the spindle within the tube. Such support devices in general are made entirely of steel and mounted via a material bond by welding the component carried on the three sides. The embodiment of the component in steel allows rigid and stable support of the forces occurring during operation in compact dimensions.
At the same time, the material has sufficient strength for direct mounting of the spindle and the transmission input shaft, and so additional bushings made of another material are not necessary.
To reduce the weight of such devices, a telescopic supporting device is proposed in DE 39 02 613 A1, where the inner and outer tubes are made of aluminum, aluminum alloy or plastic. To achieve the necessary rigidity, these tubes have longitudinal ribs.
Components, such as the spindle nut or the printing plate which are generally made of steel, must be connected to the tubes made of these same materials. A direct materially bonding connection of such these components to such a tube is only possible by gluing or soldering due to the different materials. Because of the low strength values achievable and the complexity of the processes, the processes are ruled out for telescopic tubes, which find particular use in support jacks. Other fasteners require stamping or pinning of the components for connection. In all cases, an exchange of the components requires the exchange of the respective tube.